230 WM. EEES B. ROBERTSON 



ber, about thirty-three to thirty-eight. Among these are a 

 large number of V's with transverse segmentation. He says: 

 "The small chromosomes may be derived by a breaking up or 

 'diminution' of the larger ones. Likewise the difference between 

 the somatic number and the spermatogonial number (as re- 

 ported by Duesbug, Guyer, and others) may have a similar 

 explanation." 



From the preceding survey it may be seen that V-chromo- 

 somes, with either short or long arms, are of common occurrence 

 in most families. We are led to suspect that transverse segmen- 

 tation (not always shown) and constrictions, when they occur, 

 together with non-terminal attachment of fibers may possibly 

 be correlated in many cases with decrease in numbers brought 

 about by a compounding of non-homologous chromosomes. 

 We also are led to think that a V-chromosome may break at 

 the apex to form two rods. 



3. Y-Chromosames in synapsis and reduction. A general 

 review of the literature upon these stages has been given, either 

 completely or in part, by Gregoire ('05, '10,) Haecker ('07, 

 '10), Davis ('08), Granata ('10), Wilson ('12), and others. It 

 is necessary, however, to consider the literature which bears 

 upon the V-chromosomes, since they are of such wide occurrence 

 and possible importance. I shall try to show where I think others 

 have failed to interpret correctly the behavior of these chromo- 

 somes, and wherein my work, together with the work of others 

 on these and other chromosomes, furnishes evidence in favor 

 of parasynapsis, but opposed to a complete fusion of the pairing 

 threads, also in favor of the first division being reductional. 



V-shaped chromosomes, since they are of such wide occur- 

 rence, have, I believe, played a considerable role in the debate 

 over the synapsis stages, for much confusion has resulted from 

 the failure of investigators to appreciate correctly the differ- 

 ^ ence between chromosomes of the V or J and the straight- 

 rod types during synapsis and following periods. The first 

 stage in which misunderstanding has occurred is the so-called 

 'bouquet stage.' Janssens ('03, '05), the Schreiners ('06a, '06b, 

 '08), and others have shown conclusively that, following the 



